Process for producing hollow metal articles

ABSTRACT

The invention concerns a process for producing a metallic hollow body ( 1 ), 
         in which a hollow cast part ( 1 ′) is produced by metal casting,    in which the cast part ( 1 ′) is deformed by means of internal high pressure deformation in the hollow body ( 1 ).        

     In order to improve the quality of the hollow body ( 1 ), the cast part ( 1 ′) is so produced, that it has a wall thickness distribution supporting or simplifying the internal high pressure deformation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns a process for producing metallic hollow bodies of the type set forth in the pre-characterizing portion of the main claim.

2. Description of the Related Art

DE 10244338A1 discloses a machining operation for hollow cast parts, wherein the cast part is acted upon with high pressure using an internal high pressure deforming tool. By internal high pressure deforming, the cast part is normed, in order to correct any warping produced during casting.

DE10125121A1 discloses an exhaust pipe bender, of which the individual parts are produced using deep drawing techniques.

DE19847876A1 discloses a shock absorber strut carrier or spring stit carrier, produced as a cast part.

U.S. Pat. No. 4,571,969 discloses a process for autofretage of a thick wall hydraulic cylinder by means of internal high pressure deformation.

EP0952067A2 discloses an automobile body column or support for a motor vehicle, produced by a process of pressure casting, for example, magnesium, aluminum or steel.

DE19945545A1 proposes a device for selectively deep drawing and/or pressure casting.

SUMMARY OF THE INVENTION

The present invention is concerned with the problem of providing, for a manufacturing process of the above-described type, an improved embodiment, which in particular improves the quality of the hollow body produced as a result of the process.

This problem is inventively solved by the characterizing part of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

The invention is based on the general idea, that in the first step of the process the cast part to be produced is specifically so designed, that the internal high pressure deformation to be carried out in the second step is simplified. This is accomplished by a selective distribution of wall thickness in the cast part, and namely at least in the area of the cast part involved in the internal high pressure deformation. In this manner, it becomes possible to take into consideration, for example, the flow processes in the material, which occur during high pressure deformation. In this mariner, deformations can be carried out during the internal high pressure deformation, which could otherwise not be produced or realized due to reduced wall thickness and the danger of a formation of cracks. By the corresponding design of the cast part, hollow bodies can be produced therewith by means of internal high pressure deformation, which could not be produced with a conventional internal high pressure deformation of extruded bodies of uniform material thickness.

According to one preferred embodiment, the cast part can, next to the deformation area, in which the cast part is deformed during internal high pressure deformation, exhibit at least one supply or reservoir zone, which exhibits a wall thickness which is greater relative to the adjacent neighboring area of the cast part. During internal high pressure deformation the material can flow out of the reservoir zone into the respective deformation area, whereby in the deformation area, relatively large wall thicknesses can be realized. Similarly, in the deformation area, as a result of the material flowing from the reservoir zone, a relatively strong bending or deforming can be realized.

In another embodiment, the cast pant can exhibit, adjacent to a deformation area, in which the cast part is deformed by internal high pressure deformation, at least one anchor zone, which is located at an external contour of the cast part and which cooperates during internal high pressure deformation with a matrix or die of an internal high pressure deformation tool for fixing the cast part in the matrix. In this design the cast part can be effectively fixed in the matrix during internal high pressure deformation, which improves the quality of the internal high pressure deformation and in particular, specifically limits the deformation to predetermined deformation areas. The invention here also takes advantage of the possibility of a quasi unrestricted shape for the cast part, in order to simplify or, as the case may be, improve, with a special design of the cast part, the internal high pressure deformation process.

Further important characteristics and advantages of the invention can be seen from the dependent claims, from the drawings and the associated figure description making reference to the figures.

It is understood that the characteristics described above and explained in detail below can be employed not only in the indicated combinations but rather also can be variously combined or used alone, without departing from the framework of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are represented in the figures and are described in greater detail on the following, wherein the same reference numbers indicate the same or similar or functionally equivalent components.

There is shown, respectively schematically, in:

FIG. 1. a strongly simplified sectional view showing the principal of a cast part prior to internal high pressure deformation in a segment having a deformation area,

FIG. 2. a view as in FIG. 1, however the hollow body after the internal high pressure deformation,

FIG. 3. a view as in FIG. 1, however in a different embodiment,

FIG. 4. a view as in FIG. 2, however in the case of the embodiment according to FIG. 3,

FIG. 5. a strongly simplified, principal sectional representation of a cast part prior to the internal high pressure deformation,

FIG. 6. a view as in FIG. 5, however the hollow body after the internal high pressure deformation,

FIG. 7. a strongly simplified, principal section through a casting mold, and

FIG. 8 a section as in FIG. 7, however through the cast part produced with the cast mold according to FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

According to FIGS. 1 through 8 in metallic hollow body 1 can be produced with the use of the inventive manufacturing process such that first by means of metallic casting a hollow cast part 1 is produced, which subsequently is deformed into the desired hollowed body 1 by means of internal high pressure deformation. In accordance with the invention then the cast part 1′ is so produced with the aid of the metal casting process, that it exhibits a predetermined wall thickness distribution, which is so selected, that the internal high pressure deformation process, with which the cast part 1′ is deformed into the desired hollow body, is improved and in particular is simpler to carry out. Thereby the quality of the hollow body 1 produced with the aid of the process is increased.

According to FIGS. 1 and 2, the cast part 1′ can have a deformation area 2 which is characterized thereby, that during internal high pressure deformation a deformation of the cast part 1′ takes place in it. For example, the degree of deformation differs from the deformation occurring during a directional process. For example, the cross section of the cast part 1′ during deformation consumes in the deformation area at least 10% or at least 20%. For the internal high pressure deformation, the cast part 1′ is introduced into an internal high pressure deformation tool 3. The tool 3 includes a matrix 4 for receiving the cast part 1′, which exhibits a negative image of the outer contour 10 of the hollow body 1 to be produced by the internal high pressure deformation. In the deformation area 2 this matrix 4 exhibits, for example, a recess 5, into which the material of the cast part 1′ is to penetrate during internal high pressure deformation. During internal high pressure deformation, an internal space 6 of the hollow cast part 1′ is acted upon with the necessary internal high pressure, for example, hydraulic pressure. The action of pressure on the cast part 1′ in the internal space 6 is symbolically represented by arrows in FIG. 1.

In the embodiments illustrated in FIGS. 1 and 2, the cast part 1 is provided next to the deformation area 2 next to the deformation area 2 with at least one reservoir zone 7. In the present case, two reservoir zones 7 are provided, which are located in the section plane on both sides of the deformation area 2. The reservoir zones 7 are characterized thereby, that they have a larger wall thickness relative to adjacent neighboring areas 8 of the cast part 1. For example, the wall thickness of the cast part 1′ in the respective reservoir zones 7 prior to the internal high pressure deformation is at least 50% larger than in the respective adjacent area 8, or as the case may be, in the deformation area 2. FIG. 1 shows the cast part 1′ prior to internal high pressure deformation.

During internal high pressure deformation, a widening of the cast part 1′ occurs at least in the deformation area 2. Thereby, the material from the reservoir zone 7 can now flow into the deformation area 2. The positioning and dimensioning of the reservoir zone 7 is therein specifically so selected, that the wall thickness in the deformation area 2 does not decline or declines only slightly during the deformation process. Preferably the reservoir zones 7 are so designed, that in the hollow body 1, that is, after internal high pressure deformation, a wall thickness results in the reservoir zones 7, which deviates only by 20% or less or at the most 10% from the wall thickness in the deformation area 2 and/or in the respective adjacent area 8. In the variant shown in FIG. 2, the reservoir zones 7 and the cast part 1′ are specifically so dimensioned, that the hollow body 1 after the internal high pressure deformation essentially exhibits the same wall thickness in the deformation area 2 and in the reservoir zones 7 as well as in the adjacent areas 8.

In order to further simplify the deformation process, the respective deformation area can be surrounded or enclosed by the respective reservoir zone 7, or as the case may be, the reservoir zones 7. This means, the respective deformation area 2 is circumscribed by one or more reservoir zones 7, so that during deformation material can flow from all sides out of the reservoir zones 7 into the deformation area 2.

In the embodiment shown in FIG. 1, the reservoir zones 7 are so designed, that the enlarged wall thickness is applied exclusively towards inwards, so that the external contour of the cast part 1 is not detracted from. Preferably, the respective reservoir zone 7 is here formed by a bulge, which protrudes towards inwards relative to the respective neighboring area 8.

In accordance with FIGS. 3 and 4, the cast part 1′ can supplementally or alternatively be equipped adjacent to another deformation area 2 with at least one anchor zone 9. In the present illustrative embodiment, two anchor zones 9 of this type are provided, which are located in the selected section plane on both sides of the deformation area 2. In contrast to the previously shown preferred illustrative embodiment of the design of the reservoir zones 7, here the anchor zones 9 are located at the outer contour 10 of the cast part 1′. The matrix or die 4 of the internal high pressure deformation tool 3 is provided with an anchor receptacle 11, which is shaped and positioned complimentary to the anchor zones 9. In the cast part 1′ introduced in the matrix 4, the anchor zones 9 cooperate with the anchor receptacles 11 for fixing the cast part 1′ within the matrix 4. This has the consequence, that during internal high pressure deformation essentially exclusively the deformation area 2 positioned between the anchor zones 9 is widened in the recess 5. In particular, finish processing areas 8, which with reference to the deformation area 2 are positioned on the oppositely lying side of the respective anchor zone 9, do not flow in the recess 5, whereby on each side of the anchor zones 9 shear movements and shear loads reduce the cast part 1′. This embodiment also can be used for producing a substantial improvement in quality of the hollow body 1.

Preferably, as here, the respective deformation areas 2 are surrounded or enclosed by the respective anchor zones 9, or as the case may be, multiple anchor zones 9, so that in each direction a trailing flow of material out of the adjacent areas 8 is prevented.

In the here shown embodiment, the anchor zones 9 were realized thereby, that the cast part 1′ exhibits a greater wall thickness in the anchor zones 9 then in the adjacent areas 8 or as the case may be, then in the deformation area 2.

The anchor zones 9 are here so realized, that the respective enlarged wall thickness extends essentially towards outwards. This is achieved herein thereby, that the individual anchor zones 9 respectively, are formed by a bulge, which with respect to the adjacent neighboring areas 8 project outwards. Alternatively, it is in principle also possible here to realize another embodiment of the respective anchor zones 9 thereby, that the outer contour 10 of the cast part 1 in the area of the anchor zone 9 exhibits a recess, for example, in the form of a grove. The complimentary contour piece of the matrix or die 4 then exhibits a corresponding protrusion, which engages in the respective recess in the cast part 1′ introduced in the matrix 4 in order that the cast part 1 is fixed in the matrix 4.

As can be seen from FIG. 4, the anchor zones 9 bring about that, during internal high pressure deformation, now or hardly any material can flow across the anchors on 9 into the deformation area of 2. Accordingly, the wall thickness of the hollow body 1 shrinks in the deformation area of 2.

It is noteworthy here, that the respective anchor zone 9 during internal high pressure deformation remains maintained and accordingly, according to FIG. 4, exists also in the finished hollow body 1.

In another embodiment the anchor zones 9, according to the embodiment shown in FIGS. 3 and 4, can be combined with the reservoir zones 7 according to the embodiment shown in FIGS. 1 and 2. A corresponding cast part 1′ then possesses, adjacent to the respective deformation area 2, at least reservoir zone 7 and, outside of this, at least one anchor zone 9.

In FIGS. 5 and 6 an illustrative embodiment is shown, in which the casting process for production of the cast part 1′ is so designed, that the cast part 1′ relative to the hollow body 1 is completely under-dimensioned relative to the widening achievable with the internal high pressure deformation. The cast part 1′ possesses thereby thickness deviations from the finished hollow body 1, which clearly exceed or transcend thickness or dimensional deviations, which result from the warp of the cast part 1′ during cooling. For example, the under-dimensioning of the cast part 1′ relative to the outer contour 10 of the hollow body 1, or as the case may be, relative to the inner contour 12 of the hollow body 1 is at least 5% or at least 10%. By this manner of design, in particular shapes for the finished hollow body 1 can be realized, which cannot be produced with a conventional casting process, or as the case may be, or else are not achievable by internal high pressure deformation of an extrusion press part likewise not realizable. The shape change of the hollow body 1 produceable by internal high pressure deformation of the cast part 1′ goes far beyond the directionality of a drawn cast part 1′.

In the inventive process, the final shape of the hollow body 1 is produced by the internal high pressure deformation of the cast part 1′. The internal high pressure deformation includes therewith automatically a built-in calibration process, with which the cast part 1′ is adjusted or trued. The hollow body 1 produced by the inventive process is characterized by a relatively high dimensional accuracy.

According FIGS. 7 and 8, in an advantageous embodiment of the inventive process, the respective cast part 1′ can be produced with the aid of a casting mold 13, which exhibits for example, an upper part 14 and a lower part 15. The cast mold 13 includes a hollow space 16, of which the walls form the negative shape for the outer contour 10 of the cast part 1′. In order to produce a hollow cast part 1′, a core 18 is additionally provided in the hollow space 16. In the here shown, preferred embodiment this core 18 is positioned in the cast mold 13 by means of metallic core supports 19. After the casting of the cast part 1′, the core supports 19 become integral components of the cast part 1′ according to FIG. 8. Therein the core supports 19 can, on the one hand, form-fittingly be bound in the cast part 1′. On the other hand, the core supports 19 can supplementally or alternatively be bound metallurgically in the material of the cast part 1′.

By the use of the core supports 19 remaining in the cast part 1′ a hollow cast part 1′ can be produced, which, except for a outlet opening described in greater detail below, forms a comparatively dense hollow body. In this manner, the expense and complexity of sealing the hollow cast part 1′ is reduced. A sealing of this type is necessary in order to be able to carry out the internal high pressure deformation.

Preferably the core supports 19 are intentionally so positioned and/or designed within the cast part 1′, that during finishing of the hollow body 1 they can be used as securing elements. For example, the core supports 19 can be in the form of bolts (with or without threads). In accordance therewith, for realizing the core supports 19, securing elements are preferably employed, which in the finished hollow body 1 are necessary, for example, for assembly of the hollow body 1 into a complex construction component.

According to a casting process, the core 18 must be removed from the cast part 1′. For this, the cast part 1′ can in a conventional manner be provided with here not shown outlet opening. The core 18 or, as the case may be, the core material, for example, sand, can be removed out of the cast part 1′ through this outlet opening following casting. According to a preferred embodiment of the inventive manufacturing process, now the internal high pressure deformation can be carried out by acting upon the cast part 1′ with internal high pressure through said outlet opening.

The hollow body 1 is preferably a component of a motor vehicle. For example, the hollow body 1, is a carrier or load supporting rail of a vehicle, in particular a A-column or a B-column or a C-column.

As the casting process for the production of the cast part 1, there is suited in particular manner a low pressure casting process, in which steel in particular is pressed into the respective casting mold using gas pressure. This process is particularly well-suited for producing large components with comparatively thin wall thickness. For example, achievable wall thicknesses are between 1.6 mm and 8 mm, preferably between 1.6 and 4 mm, in particular between 1.6 mm and 3 mm. One possible low pressure process is, for example, the so-called “FONT MINC (FM)”. This is a low pressure process with counter-gravity casting with use of a sand mold. In this process, the respective shape can be filled laminar, or as the case may be, with low turbulence, and comparatively rapidly. In addition, or alternatively, the melt can be acted upon with a gas pressure, in order to press the melt into the respective sand mold. In the case that the cast part 1′ is not a steel cast part, there can be employed for manufacture of the cast part 1 likewise an aluminum pressure cast processes or a magnesium pressure cast processes.

Depending upon the material of the cast part 1′ it can be useful to carry out the internal high pressure deformation, using a relatively high temperature, as a thermal internal high pressure deformation. At the same time the internal high pressure deformation process can be employed in order to subject the respective cast part to an, in certain cases, necessary thermal treatment and/or HIP (hot isostatic pressing), whereby supplemental separate manufacturing steps can be dispensed with. Particularly advantageous is the integration of supplemental work processes in the internal high pressure deformation process. For example, the internal high pressure deformation can be coupled with a trimming process, via which a not necessary part of the hollow body 1 can be separated off, without requiring for this a supplemental work step. In addition, or alternatively, the high pressure deformation can also be coupled with a stamping process, with which it is possible, for example, to remove at least one wall area out of the wall of the hollow body 1, for example in order to produce at a desired location an opening in the hollow body 1. Here also a supplemental processing step can be dispensed with.

Now that the invention has been described, I claim:

REFERENCE NUMBER LIST

-   -   1. Hollow body     -   1′. Cast part     -   2. Deformation area     -   3. Internal high pressure deformation tool     -   4. Matrix or die     -   5. Recess     -   6. Internal space     -   7. Reservoir zone     -   8. Adjacent area     -   9. Anchor zone     -   10. External contour of (1)     -   11. Anchor receptacle of (4)     -   12. Internal contour of (1)     -   13. Cast mold     -   14. Upper part of (13)     -   15. Lower part of (13)     -   16. Hollow space of (13)     -   17. Wall of (13)     -   18. Core     -   19. Core support 

1. A process for producing a metallic hollow body (1), including the steps producing a hollow cast part (1′) by metal casting, such that the cast part (1′) includes a deformation area (2) which is to be subsequently deformed by internal high pressure deformation, and has at least one thereto adjacent reservoir zone (7), which has a thicker wall thickness relative to the deformation area (2) than the adjacent neighboring area (8) of the cast part (1′), so that the distribution of the wall thickness supports or simplifies an internal high pressure deformation, deforming the cast part (1′) by internal high pressure deformation to form the hollow body (1).
 2. A process according to claim 1, wherein a cast part (1′) is produced, in which the respective deformation area (2) is surrounded by the reservoir zone (7) or by multiple such reservoirs zones (7), and/or in which the respective reservoir zones (7) are formed by respective bulges protruding relative to an adjacent area (8), and/or in which the respective reservoir zone (7) exhibits an enlarged wall thickness only towards inwards with reference to the mold core.
 3. A process according to claim 1, wherein the cast part (1′) and the internal high pressure deformation area are so designed, that in the hollow body (1) the wall thickness in the deformation area (2) and in the respective reservoir zone (7) are the same following the internal high pressure deformation, or that after the internal high pressure deformation the hollow body (1) exhibits approximately the same wall thickness in the deformation area (2) and in the respective reservoir zone (7), or that after the internal high pressure deformation the hollow body (1) exhibits the same wall thickness in respective adjacent areas (2) and in the respective reservoir zone (7), or that prior to the internal high pressure deformation the wall thickness in the reservoir zone (7) is at least 50% larger then in the deformation area (2) and/or in the adjacent area (8), or that the wall thickness in the reservoir zone (7) after the internal high pressure deformation is maximally 10% larger or smaller than in the deformation area (2) and/or then in the adjacent area (8).
 4. A process according to claim 1 comprising forming on said cast part (1′), adjacent to a deformation area (2) in which the cast part (1′) is deformed during internal high pressure deformation, at least one anchor (9), which is located on an outer contour (1) of the cast part (1′), introducing said cast part (1′) into a mold having a matrix or die such that said anchor is in mating engagement with a recess (4) adapted to receive said anchor zone, and subjecting said cast part (1′) to internal high pressure deformation, whereby during internal high pressure deformation said anchor (9) cooperates with said matrix or die (4) of an internal high pressure deformation tool (3) for fixing the cast part (1′) in the matrix or die (4).
 5. A process according to claim 4, wherein the cast part (1′) is produced, in which the respective deformation area (2) is surrounded by the anchor zone (9) or multiple such anchor zones (9), or in which the respective anchor zones (9) relative to an adjacent neighboring area (8) of the cast part (1′) exhibit a greater wall thickness, or in which, in the respective anchor zones (9), the enlarged wall thickness is directed only towards outwards, or in which the respective anchor zones (9) are formed by a bulge projecting towards outwards from the respective neighboring area (8), or in which the respective anchor zones (9) are formed by a recess formed in the outer contour (10).
 6. A process according to claim 5, wherein the internal high pressure deformation is continued only so long, that the respective anchor zone (9) continues to remain on the hollow body (1) even after the internal high pressure deformation.
 7. A process according to claim 2, wherein a cast part (1′) is produced, which has, next to a deformation area (2), at least one reservoir zone (7) directed inwards and at least one anchor zone (9) directed outwards.
 8. A process according to claim 1, wherein a cast part is produced, in which the cast part (1′) is produced completely under-sized or undersized relative to the hollow body (1) or, in which the outer dimensioning, relative to the outer contour (1) and/or relative to the inner contour (12) of the hollow body (1), is at least 5%.
 9. A process according to claim 1, wherein the cast part (1′) is produced using a core (18), which is positioned in a hollow space (18) of a cast mold (13) using metallic core supports (19), and/or an outlet opening of the cast part (1′) is provided, through which a core (18) or a core material can be removed out of the cast part (1′) subsequent to casting, said opening for acting upon the cast part (1′) with internal high pressure during internal high pressure deformation, and/or at least one of the core supports (19) remains in the finished hollow body (1) as a securing element, and/or as the core support (19), a securing element is employed, which is a part of the finished hollow body (1).
 10. A process according to claim 1, wherein the cast part (1′) is a thin-wall cast part, and/or that the cast part (1′) is a steel cast part or a light metal cast part, in particular, an aluminum cast part or a magnesium cast part.
 11. A process according to claim 1, wherein the internal high pressure deformation is carried out as a thermal internal high pressure deformation, and/or the internal high pressure deformation is coupled with a trimming process for trimming at least a part of the hollow body (1), and/or the internal high pressure deformation is coupled with a stamping process for removing at least one wall area out of the wall of the hollow body (1). 